Sound picture apparatus



July 16, 1940. H. ROBINSON sormn PICTURE APPARATUS Filed June 3 1938 2 Sheets-Sheet l I. IL

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H. l. ROBINSON SOUND PICTURE APPARATUS 2 Sheets-Sheet 2 Filed June 3, 1938 Bummer @maffiiirmm Gttorneg Patented July 16, 1940 'UNlTED STATES PATENT OFFICE SOUND PICTURE APPARATUS Hyman I. Robinson, Philadelphia, Pa., assignmto Radio Corporation of America, a corporation of Delaware.

Application June 3, 1938, Serial No. 211,543

Prior to the Pesce invention the practice was to locate the volume controlin the amplifier.

This practice precluded ume control for the incoming machine, since the a pre-setting of the volvolume control had to be retained in circuit until the outgoing machine was disposed of. In other types of such apparatus separate volume controls for the several machines were provided, which required volumecontrol at low levels, thereby introducing noiseQand which prevented a unified volume control permitting of remote control.

In the above'i-dentified application Pesce 1ocates the volume. control between the voltage amplifier and the power amplifier, provides a separate volume control for each projector, and

provides means for switching the volume controlssimultaneously with the projector.

A principal object of the present invention is to provide a single control for a plurality of the operating condition thereof.

Another object. of the invention is to .produce a simple, compact, inexpensive, and trouble-free device for adjusting'the output level of one or more sound reproducers, said device being capable of being preset to a position determined by the operating characteristics of the reproducer with which it is associated, and likewise capable of being readjusted, with respect to said preset position, from a remote point.

Other objects and advantages, together with certain details of construction, will be apparent and the invention itself will be best understood by reference to the following specification and to the accompanying drawings, wherein Figure -1 ,is a schematic diagram =01 a threeunit sound picture apparatus including. Pesces switching arrangement and showing the several in accordance with the invention.

principle of the present Figure 2is.a sectional elevation of a mechanism including a clutch, for actuating the several volume controls of Fig; 1,

Figure 3 is a sectional view taken on the line 3--3 of Fig. 2, and

Figure 4 is a detailed view of the clutch of 5 Fig. 2. y

In the drawings, the input from the several soundheads is represented as being fed through the three transformers T1, T2 and T3, which are connected in series. The output from these transformers is fed to a rotary switch S1 which short-circuits the output from the two :soundheads which are not in service. The output from the soundhead in service, which, in the position 16 0f the switch illustrated, is the one associated with transformer T2, is fed to the voltage amplifier' V. Output from the voltage amplifier V is transmitted to a second rotary switch S2 and is selectively directed to the several attenuators A1, 20 A2 or A3, as may be required. These attenuators are illustrated as a modified T-pad type of attenuator, but it will be apparent to those skilled in the art that H-pads or any other equivalent type of attenuator may be substituted therefor. 5

In the position of the switch S2 shown, which matching the'soundhead of unit T2 in the circuit, corresponds, to the position of the switch S1 the output from. the switch S2 passes to the at-. tenuator A2. The output from this attenuator 30 A2 passes through the leads an and 1.02 to a third rotary switch S3 which in turn connects, through the leads 103, to the link circuit L. The output from the link circuit L passes in the usual manher; through the power amplifier P. A. to the 35 loudspeaker or loudspeakers L. S.

The three controls of each of the T-pads indicated are interconnected, as indicated schematically in Fig. '1, so that the three resistors are changed in value simultaneously. Each of these attenuators A1, A2, A3 is connected through an appropriate clutch C1, C2 and C3, to a centralized control unit M, which may be a capacitor motor, selsyn motor, or solenoid control device adapted to be controlled from some remote point, such as an auditorium. This connection between the several attenuators may likewise be provided in the thatthey may be preset in accordance with the volume indications on each reel of film by releasing the corresponding clutch C1, C2 or C3 and adjusting the attenuator of the incoming ma- 55 Figs. 2, 3 and 4 show a preferred form of mechanism for adjusting the several attenuators separately or together. Each attenuator A is enclosed in a rigidly supported housing l9 through which a rotatable shaft l2 extends. Mounted on a sleeve M, which is supported on shaft I2 for relative rotation therewith, are two spring arms I6 and 18 which engage suitable attenuator contacts 20 and 22, respectively, shown fixed on the front panel of the housing I6. It would-needlessly complicate the drawings to show the various details of resistors to which the contacts 20 and 22 are connected.- A ball 23, which is biased by a spring 26 against a pinion 28 which has as many slots as there are contacts 22, ensures a step-bystep movement of the sleeve I l.

A second sleeve 30 is mounted for rotation and for axial movement adjacent one end of shaft 12-. a

Sleeve 30 supports a knob k" and terminates in a clutch C element which may conveniently be in the form of a toothed wheel 82 through the hub of which the control shaft I2 extends. Shaft 2 terminates in a complementary toothed clutch element 34 which is shown'flxed to the shaft l2 by a screw 36.

The clutch elements 32 and 36 are normally held in engagement by a spring 38 which surrounds the sleeves It and 30.

The slidable sleeve 30 terminates in a spline 60 which at all times is connected in torque transfer relation with sleeve id through a complementary spline c2 thereon. Fixed on the opposite end of shaft I2 is a bevel gear 443 which meshes with a similar gear 46 on the shaft 68 which, as indicated in Fig. 1, is connected with the shafts of the other attenuators.

With the clutch elements 32 and 34 engaged as shown in Fig. 2, the knob k is connected both to the sleeve 14, on which the contact arms l6 and I8 are mounted, and to the shaft l2. Knob k therefore controls the relative setting of all the attenuators simultaneously. On the other hand, when knob is is pushed in on its slidable sleeve 30 against the bias'of spring 38, as shown in Fig. 4, the clutch elements 32 and 36 are disengaged so that turning of the knob imparts torque to sleeve 36 and no torque whatsoever is transmitted to shafts l2 and '38.

The preferred practice is to preset each attenuator separately to achieve a desired relative or uniform output level for all the sound reproducers. Since certain of the parts of the sound reproducers, for example, the photocells, may not exhibit perfectly matched electrical characteristics, the initial setting of the contacts of the several attenuators may be different.

After all of the attenuators are preset, the control knob of the machine in use will ordinarily be employed to vary the output level. This-is done with the clutch elements engaged so that the incoming machine is adjusted and continues at the desired sound level.

What is claimed is:

Apparatus of the type described comprising a plurality of electrical sound reproducers, a plurality of adjustable volume controls corresponding to the number of reproducers, control 'shafts individual to said volume controls, a common shaft connecting the individual shafts in mutual torque transfer relation, a sleeve on each individual shaft and connected in permanent driving rela- HYMAN I. ROBINSON. 

